For the production of semiconductor components, doped semiconductor substrates are used as a starting point. Typically, such a conventional semiconductor substrate is a wafer. From such a wafer, a number of semiconductor chips can be produced. Hence, the yield of semiconductor chips increases with the size of the wafer. Alternatively, only one semiconductor chip can be produced from the whole wafer, for instance a power thyristor or a power diode. In this case, an increased size of the wafer allows for the production of power semiconductor chips having an increased ampacity.
As a wafer typically has the shape of a flat, round disk, the size of a wafer usually is indicated by its diameter. At present, wafers having diameters of up to 300 mm are available on the market, but only with a p-doping. However, for the production of many kinds of semiconductor components like “drain-down” transistors it is advantageous to start on the basis of an n-doped substrate. In a drain-down” transistor, gate and source are commonly arranged on a front side of the transistor and drain on a rear side opposite the front side. In view of the above-mentioned advantages of large area semiconductor substrates there is a need for n-doped large area substrates but also for p-doped large area substrates.